solid state col r tel or colordaptor

[cbenham]

Originally Posted by vintagecollect

Has ANYONE used the original 2 tube setup for motor sync using AC motor w new ss adapter??? I figure the most expensive part to build circuit is power xfrmer unless someone has a junk box w/ spare power transformers. HOW WOULD someone use red signal to original colodapter sync circuit?? Would a pre amp circuit be needed. I have a clean copy of schematic if someone wants this in good detail. Any ideas

I've breadboarded several different Colordaptor Servo and TRITCH circuits and adapted them to do the color switching and wheel control for a Col-R-Tel disk and chassis, where the original printed circuit switch and brush system had been destroyed.

While it worked, it was very iffy and not very stable. The wheel would lose sync when the air conditioner started. A big, hot, heavy SOLA constant voltage sinusoidal transformer makes it work OK.

By the way, the TRITCH circuit is very critical to make work. The hardest part is to find the three equal 560K grid return resistors. They don't need to be *Exactly* 560K but they do need to be precisely *EQUAL* in value.

The Colordaptor system uses an audio output transformer to control the motor speed. I've also substituted a vertical output transformer [the 4 lead type, not a 3 wire autoformer] and it worked about the same as I described above.

The only power needed for the Colordaptor servo is a few mils of plate B+ for the 12AT7.

The 6AQ5 doesn't actually draw current from the power supply. It is configured as a half wave grid controlled rectifier. The harder it conducts, the lower the voltage drop across the secondary of the transformer and the faster the motor goes.

HINT: place a 1000 volt full wave bridge rectifier between the transformer primary and it's connections to the 6AQ5 Plate and Cathode. Doing this changes it to a full wave grid controlled rectifier. This works better than the original halfwave version.

As for detecting the red field pulse coming from Darryl's converter, I designed
a transistorized version of the original tube type red pulse detector that's in the Gray Research CBS monitor at ETF.

I built two of these for the CBS sets I displayed at the ETF Convention last year.

The red field pulse is in the same place in the sync signal in both of Darryl's converters, the CBS and the NTSC.

While I've not built one to work with the NTSC converter YET, I'm about to do so because I have a project that needs one.

At this point the only difference I think I'll find is the need to retune the detector tank circuit from the CBS frequency of 58.320 KHz to the NTSC frequency of 31.462 KHz.

The detected red field pulse is the signal that would feed the Colordaptor servo circuit, and be compared to the wheel pulse in the 12AT7 controlling the motor speed through the 6AQ5 and the output transformer.

More as time allows...

Film@Eleven.

Cliff